The present invention relates to a process and a circuit arrangement for controlling the use of satellite transmission capacity for the substitution of out-of-order data lines in terrestrial networks, respectively.
Switched trunk groups in voice and data networks are generally operated in a two-way alternate manner between computer-controlled switching devices. With this mode of operation, both switching devices are able, independently of each other, to access and occupy unoccupied trunks of the group. If certain data lines go down completely, this also permits automatic alternative routing to an unoccupied and operable data line of a terrestrial network.
The known traffic management processes are summarized and outlined in CCITT Recommendation E.412: “Network Management Controls” (10/92). However, it is also known to remedy out-of-order data lines in terrestrial networks by using spare satellite transmission capacity. Particularly with regard to the access lines, alternative routing via satellite requires a manual initiation after a transmission capacity request has been sent to a central station, a backward channel which is carried via terrestrial lines or via satellite being used for this purpose.
The manual initiation of alternative routing according to the related art is time-intensive. It may even be necessary for connection configurations to be transmitted to the locations involved, and a backward channel must be reliably available in the case of an alternative routing request. This may lead to problems,—particularly in the case of a terrestrial backward channel, for example, if the backward channel and user information channel are carried in one access line—because no backward channel is directly available.
German Published Patent Application No. 43 08 161 describes a system for telecommunication via satellites, which utilizes at least one transmitting station and at least one receiving station, and at least one monitoring circuit for monitoring the signal transmitted from a transmitting station via the satellite link and received by a receiving station. In response to interference of the signal, an alternative link results because provision is made for at least one network module which automatically produces a communications link between a transmitting station and a receiving station via a switched network when one parameter of the signal assumes critical values caused, for example, by weather, and which releases this link again when the parameter of the signal assumes uncritical values. Thus, this system is clearly limited to the monitoring of transmission quality in satellite systems, with the possibility of switching automatically to fixed networks when quality deficiencies have been ascertained in the signal.
In addition, in Japanese Laid-Open Patent Application No. 01 293020, a method is described for replacing defective satellite transmission channels by lines of fixed networks. Just as the method described above, this method is not usable for the case when lines of a fixed network break down and free transmission capacity of satellite systems is used for them.